I don't get it, either.
My mom explained to the little kid me that Noah only took a few animals and they went on to make the different variations we see today.
Maybe Noah did some selective breeding and got divine pedigrees for his umm...creations.
Mate spiders with crabs and you get the scorpion.
Sheep + camel = llama
Prisoner + horse = zebra
Beaver + duck = platapus
What others are there?